Unpopular opinion, but I think quite a few areas of the game plummeted when they opened up cross-world travel. It's handy if you have friends spread around and don't want to transfer, but it seems to be causing problems in just about every other aspect. I don't really know how they could address it without either a) removing it entirely or b) merging everything as you suggest, but as little as I know about that sort of thing, previous information makes it seem pretty much impossible. I also have a vague suspicion NA raiders and RPers wouldn't be jazzed about sharing a PF if current complaints are anything to go by...

(And it's "inherently", btw.)